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Indications and Contraindications The indications for use of locking plates include the following: 1 metaphyseal and intra-articular tures; 2 highly comminuted frac-tures, particularly t

The Use of Locking Plates

in Fracture Care

Since the advent of surgical frac-ture care, orthopaedic surgery has seen many great advances The invention of intramedullary nailing

by Kuntscher in the 1940s marked the beginning of a new approach to the treatment of long bone fractures

The circular external fixator devel-oped by Ilizarov in the 1950s added greatly to fracture care and limb lengthening The dynamic compres-sion plate developed by Perren allowed for rigid fixation of both extra- and intra-articular fractures, permitting early joint motion and re-turn of function The concept of

rig-id and anatomic fracture reduction became the goal for many surgeons

This approach, however, sometimes sacrificed the biology of the fracture and failed to protect the blood sup-ply of the bone in an effort to pre-cisely reduce and fix each fracture fragment.1,2The technique of locked plating, developed in Davos, Swit-zerland, in the 1990s,1has been de-scribed as a “revolution” in fracture care.3

Locked plating refers to the fact that the screw heads are threaded and, when tightened, lock into threads in the plate By locking the screws into the plate, a fixed-angle construct is created that is much less prone to loosening or toggle than traditional nonlocked plates ( videos 1, 2, and 3) Recent terms

such as percutaneous plating, submuscular plating, minimally in-vasive plate osteosynthesis, and bridge plating refer to techniques of plate placement; although they are commonly used with locked plates, these terms are not synonymous

Percutaneous plating, submuscular plating, and minimally invasive plate osteosynthesis mean that the plate is placed through small

inci-sions with as little dissection and stripping of the soft-tissue envelope

as possible Bridge plating refers to a plate in which several screw holes are left open at the level of the fracture (Figure 1) Locked plating simply means that the screws lock into the plate regardless how the plate is inserted An unlocked plate means that the screw is not firmly attached to the plate, and toggling

of the screw can occur through bone ( video 4).

Indications and Contraindications

The indications for use of locking plates include the following: (1) metaphyseal and intra-articular tures; (2) highly comminuted frac-tures, particularly those involving diaphyseal and metaphyseal bone; (3) osteoporotic bone; (4) proximal tibia and distal femur fractures; and (5) periprosthetic fractures.4 Theoret-ically a locking plate could be used anywhere a traditional plate is ap-plied Locking plates have an advan-tage with fractures in osteoporotic bone, where loss of fixation is a con-cern.5 Highly comminuted diaphy-seal or metaphydiaphy-seal fractures often can be spanned or bridged by a locked submuscular plate (Figure 1) Locked plates offer an advantage in unstable fracture patterns that tradi-tionally required dual plating, such

as bicondylar tibial plateau frac-tures.4,6 Proximal third tibia frac-tures have a high malunion rate with intramedullary nailing; locked plat-ing may be advantageous with these fractures, as well.7,8

Locked plates have been designed for the treatment of most periarticu-lar fractures and are precontoured to fit Less Invasive Surgical

Stabiliza-Robert V Cantu, MD

Kenneth J Koval, MD

Dr Cantu is Assistant Professor,

Orthopaedic Surgery,

Dartmouth-Hitchcock Medical Center, Lebanon,

NH Dr Koval is Professor, Orthopaedic

Surgery, Dartmouth-Hitchcock Medical

Center.

None of the following authors or the

departments with which they are

affiliated has received anything of value

from or owns stock in a commercial

company or institution related directly or

indirectly to the subject of this article:

Dr Cantu and Dr Koval.

Reprint requests: Dr Cantu,

Dartmouth-Hitchcock Medical Center, One Medical

Center Drive, Lebanon, NH 03756.

J Am Acad Orthop Surg

2006;14:183-190

Copyright 2006 by the American

Academy of Orthopaedic Surgeons.

The video that accompanies

this article is “The Use of

Lock-ing Plates in Fracture Care,”

available on the Orthopaedic

Knowledge Online Website, at http://

www5.aaos.org/oko/jaaos/surgical.cfm

tion (LISS) plates (Synthes, West

Chester, PA) and Locking

Compres-sion Plates (Synthes) are locked

plates designed specifically for

peri-articular fractures9 (Figure 2) Used

for malunions, locking plates act as

a fixed-angle construct to hold

align-ment as well as to provide increased

stability Combination plates (plates

with holes for both locked and

non-locked screws) can be used for

cer-tain nonunions, such as

hyper-trophic nonunions, both to compress

the fracture and provide increased

stability ( videos 5 and 6).

There are few absolute

contraindi-cations to the use of locked plates

Relative contraindications include

the following: (1) fractures best

served with fixation other than plates

(eg, patella fracture); (2) fractures in

which the soft-tissue injury

pre-cludes immediate plating (eg, Gustilo

grade IIIB or IIIC tibia fracture);

(3) simple fracture patterns that do not require either unlocked or locked plates; and (4) fractures that would require bending of precontoured locked plates Because of the in-creased cost of locked plates com-pared with traditional nonlocked ones, use of locking plates should be reserved for instances in which they are clearly advantageous

Surgical Techniques

Traditional open approaches can be

used with locking plates ( video 7) The technique of fracture

expo-sure and reduction is similar to that used with nonlocked plates Tempo-rary fracture reduction with clamps

or Kirschner wires (K-wires) is fol-lowed by application of the plate

The primary difference with a lock-ing plate is the technique of screw insertion With nonlocked screws, the surgeon has tactile recognition when the screw purchases the far

cortex and pulls the plate against the bone This sensation helps the sur-geon know the quality of the bone and ensures that the screw is of ap-propriate length This sensation is lost with locking screws because the screw is inserted until it locks into the plate Screw length must be care-fully determined before insertion Another difference is that the locked screw can be inserted only in a fixed angle Proper plate position and loca-tion are important to ensure that the screws do not engage any neurovas-cular structures

The insertion techniques for many locked plates, such as the LISS plate, are an important advance in fracture treatment By placing the plates in a minimally invasive man-ner, the soft-tissue envelope around the fracture is preserved Fracture re-duction can be difficult when using minimally invasive techniques and a locking plate Articular fragments still require direct visualization and rigid fixation before plate placement

Figure 1

A locked plate bridging a highly

comminuted femur fracture Several

screw holes are left open over the

comminuted portion of the fracture site

(Adapted with permission from

Synthes, USA, West Chester, PA.)

Figure 2

A, Less Invasive Surgical Stabilization (LISS) plate B, Locking Compression Plate.

(Reproduced with permission from Synthes, USA, West Chester, PA.) Use of Locking Plates in Fracture Care

An example is a distal femur fracture

with an intra-articular

exten-sion.9,10A parapatellar incision is

re-quired to reduce and fix the articular

fragments Following articular

frac-ture reduction, the locked plate can

be placed in a submuscular fashion

along the lateral cortex, avoiding

dis-ruption of the fracture biology in the

metaphyseal region (Figure 1)

For extra-articular metaphyseal or

diaphyseal fractures, locked plates

can be placed through minimal

inci-sions An example is a periprosthetic

metaphyseal femur fracture (Figure

3) A 5- to 7-cm lateral incision is

made over the distal femur and

car-ried down through the tensor fascia

(Figure 4) The periosteum is elevated

off the lateral epicondyle of the

dis-tal femur The fracture itself is not

exposed; rather, an indirect reduction

is performed Manual traction

com-bined with use of appropriately

placed bumps can restore proper

length, rotation, and alignment of the

fracture Additionally, an external

fixator or the universal distractor can

be applied to hold the reduction (Fig-ure 5)

Next the locked plate is slid along the lateral cortex of the femur in a submuscular fashion A separate

2-to 3-cm incision can be made at the proximal extent of the plate This al-lows insertion of an elevator or a fin-ger to ensure that the plate is

proper-ly positioned on the lateral cortex in the anteroposterior dimension Most locked plates have a targeting arm that allows for temporary fixation of the plate using K-wires both proxi-mal and distal to the fracture (Figure 6) Some targeting arms allow inser-tion of a K-wire just proximal to the plate (Figure 7, A and B) This wire

Figure 3

Preoperative anteroposterior (A) and lateral (B) radiographs

of a comminuted, periprosthetic distal femur fracture

Figure 4

Intraoperative view of a lateral incision of the distal femur The soft-tissue envelope at the level of the fracture is not violated Because the fracture is extra-articular, no parapatellar arthrotomy is required

Spanning external fixator before plating The fixator was used for temporary stabilization while soft-tissue swelling decreased The fixator can be left in place

or adjusted to aid in fracture reduction during definitive internal fixation

Figure 5

should be placed parallel to the joint surface to ensure proper varus-valgus orientation (Figure 7, C) Intraoperative fluoroscopy is es-sential to judge fracture reduction and hardware placement (Figure 8) With the LISS system, the whirlybird, or push-pull device, can be inserted to improve fracture reduction and pull the bone closer to the plate (Figure 9) Because locked plates do not rely on bone contact for fixation, it is not nec-essary to pull the bone tightly against the plate (Figure 10) For this reason, locked plates have been called inter-nal exterinter-nal fixators

Once provisional reduction and fixation have been achieved, place-ment of locked screws can be per-formed Several systems employ self-drilling and self-tapping screws, which can be placed using a power

Figure 6

Placement of proximal K-wire in the proximal femur The index finger of the right hand

placed in the incision helps to ensure that the plate is properly positioned on the

femur Outside of view, traction is being maintained to hold the length and

alignment

Figure 7

A,Placement of provisional distal K-wire The plate is centered on the lateral cortex of the distal femur The K-wire

is placed parallel to the joint surface B, Submuscular

placement of a LISS plate A targeting device can be used

as a handle to help position the plate on the lateral cortex of the femur The soft-tissue envelope at the fracture level is

intact C, Intraoperative fluoroscopic view demonstrating the

provisional K-wire The K-wire is placed parallel to the joint surface

Use of Locking Plates in Fracture Care

Figure 8

Intraoperative fluoroscopic view showing the plate off the

femur bone with the provisional K-wire External fixation pins

are visible to the left of the K-wire

Figure 9

Use of the whirlybird, or push-pull device The whirlybird pulls the bone toward the plate, decreasing the distance between the plate and the bone, improving fracture reduction

Figure 10

Intraoperative fluoroscopic view after the whirlybird

tightening

Figure 11

A power drill is used to place the self-drilling, self-tapping screws Note the K-wires holding the length and the bump of folded towels under the thigh to maintain alignment

Figure 12

Postoperative anteroposterior (A) and lateral (B)

radiographs demonstrating overall restoration

of length, alignment, and rotation Rather than expose and reduce each fracture fragment, the construct was used to bridge the fracture comminution

drill (Figure 11) It is important that

proper plate position and screw length

be determined before the screws are

inserted With a distal femur fracture,

multiple screws can be placed

prox-imal and distal to the fracture using

the targeting device (Figure 12) As

mentioned, several screw holes

typ-ically are left open at the level of the

fracture to create a bridging construct

If every screw were to be inserted, the

fixation would be overly rigid, and

only primary bone healing would

oc-cur A minimum of three unicortical

screws should be placed distal to the

fracture The unicortical screws are

placed through small stab incisions

The soft-tissue sleeve can be placed

through the targeting arm to

deter-mine the exact location of these

in-cisions Once definitive fixation is

achieved, the incisions are irrigated

and closed Early range of motion can

be started, but weight bearing

typi-cally is delayed a minimum of 4 to 6

weeks or until radiographic evidence

of healing

Outcomes

Locking Plates

Some of the earliest studies on

locking constructs looked at

infec-tion rates Of 1,229 applicainfec-tions of

the PC-Fix in one prospective,

mul-ticenter trial, the overall infection

rate was only 1.1%.7The infection

rate for open fractures was 1.6%

These results correspond with those

of animal studies.7The same authors

compared the PC-Fix to a dynamic

compression plate on tibia fractures

in rabbits After plate application, an

inoculum of bacteria was injected

around the plate The PC-Fix

con-structs required 10 times as many

bacteria to create clinical infection.7

Biomechanical testing of locking

plates has shown favorable

out-comes compared with nonlocking

plates One of the earliest

biome-chanical studies for fixation of distal

femur fractures compared a standard

condylar buttress plate and a 95°

blade plate with a locked condylar

Pearls and Pitfalls

Soft-Tissue Dissection and Fracture Exposure

• Articular fractures require open exposure to permit anatomic reduc-tion With metaphyseal and diaphyseal fractures, however, the goal

is to minimize soft-tissue dissection at the level of the fracture Ca-daveric studies have shown a significant improvement in maintain-ing the perforatmaintain-ing arteries of the distal femur when percutaneous plate insertion was compared with traditional open placement.11

Fracture Reduction

• Locked plates are not a justification for inadequate fracture reduc-tion Newer locking plates allow for placement of either a locked or nonlocked screw through so-called combination holes With these plates, a nonlocked screw can be placed in a lag fashion to help with fracture reduction With plates that provide only locked holes, frac-ture reduction must be achieved before screw placement

• Reduction aids include using various-sized bumps, manual or me-chanical traction, or a temporary external fixator or the universal distractor Schanz pins can be used to manipulate fragments, and the self-drilling, self-tapping whirlybird can be used.12 Universal T-handle chucks (Synthes) placed over the provisional K-wires and tightened against the stabilization bolt sleeves also obtain

provision-al reduction.12

Locking Plate Application

• Once adequate anatomic reduction has been achieved, locking plate fixation can be applied Most locked plates are designed to be placed

in a submuscular fashion If the plate has a targeting device, this can

be used to help manipulate the plate into proper position Fluoros-copy is also helpful in judging proper plate position (Figure 7, A)

• A 2- to 3-cm incision at the end of the plate allows a finger to be placed, ensuring that the plate is centered on the bone

• When using combination plates, any nonlocked screws should be placed before locked screws Once a locked screw has been placed, the distance between the bone and the plate is fixed and cannot be changed with a nonlocked screw

The LISS System

• LISS system screws are self-drilling and self-tapping They are placed

in a unicortical manner, eliminating the need to measure screw depth

In the metaphyseal region, screw length is based on the size of the patient’s condyles as measured on preoperative radiographs or by plac-ing K-wires and measurplac-ing their depth In the diaphyseal region, screw length should be shorter than the width of the medullary canal; oth-erwise, the screw will not completely seat in the plate if the screw tip contacts the opposite cortex

• The whirlybird is used before placing locked screws (Figures 8 and 9)

• When using the 13-hole tibial LISS plate, the superficial peroneal nerve is at risk with percutaneous insertion of screws 11 through

13.13It is recommended that a larger incision be used at this level and careful dissection be performed to protect the superficial pero-neal nerve

Use of Locking Plates in Fracture Care

buttress plate The locked plate

showed greater fixation stability in

axial loading both before and after

cyclic loading.16Biomechanical tests

have shown that many of the factors

that influence stability of an

exter-nal fixator apply to locked plates

Factors such as bone contact,

work-ing length or distance of the first

screw to the fracture, number of

screws, and distance of the plate to

the bone all contribute to rigidity of

the construct In one biomechanical

test, leaving one screw hole open on

either side of a fracture resulted in a

doubling of the flexibility of the

con-struct in both compression and

tor-sion.17As mentioned, in many

appli-cations, some flexibility is desirable

to stimulate callus formation and secondary bone healing

LISS Plates

Most outcome studies on LISS plates have shown favorable results

In one retrospective review of 123 distal femur fractures treated with the LISS system, 93% healed with-out bone graft, the infection rate was 3%, and there was no loss of distal fixation.18In a prospective study of

38 complex proximal tibia fractures treated with the LISS system, 37 (97%) healed with satisfactory align-ment, there were no infections, and the average lower extremity

mea-sure score was 88.19Another review

of 77 proximal tibia fractures treated with the LISS system showed that

70 (91%) healed without complica-tion.20 The overall union rate was 97%, with an average time to full weight bearing of 12.6 weeks The infection rate was 4%.20

LISS plates also have shown fa-vorable results in biomechanical tests One cadaveric study compared the LISS plate with a condylar but-tress plate and a dynamic condylar screw for supracondylar femur frac-tures Under physiologic loading conditions, the LISS construct con-sistently showed less irreversible de-formation than did the other two.21 Another biomechanical study com-pared the tibial LISS plate with dual plating of simulated Schatzker type

VI tibial plateau fractures After re-petitive loading, no statistical differ-ences between the two constructs were found.22

Summary

Locked plating represents a major ad-vance in fracture care Advantages over traditional plating include im-proved construct stability, targeting devices that permit percutaneous in-sertion of screws and preservation of fracture biology, and, in some studies, higher union rates with lower infec-tion rates.18-20As with any new tech-nique, there is a learning curve for fracture reduction and implant inser-tion When using percutaneous tech-niques, fracture reduction may prove

to be more challenging than with tra-ditional open incisions A locked con-struct is not a justification for im-proper fracture reduction Compared with nonlocked plates, removal of locked plates may be more difficult and often requires larger incisions and special extraction devices

References Citation numbers printed in bold type indicate references published

within the past 5 years

Pearls and Pitfalls

Plate and Screw Removal

• Although LISS plates can be inserted percutaneously, removal may

require a larger incision Stripping of the screw heads is a common

occurrence when removal is attempted percutaneously.14

• One technical trick is to interpose the foil from a suture pack

be-tween the screw driver and the screw head in an attempt to improve

the connection.15If this does not work, the conical extraction screws

for the 4.9-mm locking bolts in the Synthes Screw Removal Set (no

309.530) can be used to remove the stripped screws

• Multiple extraction screws may be required because they often

can-not be easily removed from the LISS locking bolts after extraction

• Sometimes the conical extraction screw may fail to engage the

stripped screw When this happens, a high-speed burr can be used to

cut the plate around the screw head

• Once the plate is removed, the stripped screws can be removed

us-ing the extraction forceps in the Synthes Screw Removal Set.14

Locking Plate Position

• When using precontoured plates on the distal femur, it is necessary

to place the plate on the lateral aspect of the condyles If the plate

is placed too anterior, the fixed-angle screws may aim too far

poste-rior Also, if the plate is placed too anterior, the plate may sit

ante-riorly off the proximal femur Matching the precontoured plates to

the curve of the condyles is important to restore proper varus-valgus

alignment

Bridging Plates

• A potential pitfall when treating highly comminuted fractures is

plac-ing too many screws To achieve a bridgplac-ing construct and secondary

bone healing, a plate of sufficient length is needed and a minimum

of 2 to 3 screw holes must be left open at the level of the fracture

If part of the plate is not left open, the plate will not have sufficient

flexibility to permit micromotion and subsequent callus formation

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Use of Locking Plates in Fracture Care